If you look on the label of conventional “lipoic acid” supplements, you’ll see just that: “lipoic acid” or “alpha-lipoic acid,” and the number of milligrams per capsule or tablet. What the label won’t tell you is that you’re actually getting a 50/50 mixture of two different, mirror-opposite opposite isomers of lipoic acid in such supplements. When a molecule exists in just two isomers, and those isomers are one another’s exact opposites – as is the case with lipoic acid – the two isomers are called “enantiomers.”
Of the two isomers of lipoic acid present in conventional supplements, the enantiomer which is identical to the one made by living things for their use – the natural form of lipoic acid – is the “R(+)-enantiomer,” or “ R(+)-lipoic acid.” “S(-)-lipoic acid” is a purely artificial molecule: it does not exist in nature but is produced as a byproduct in the normal method of producing commercial lipoic acid (see Figure 1).
A 50/50 mix of two enantiomers is called a “racemic compound” or “racemate,” and so the proper, scientific designation for the lipoic acid in conventional supplements is “rac-lipoic acid,” “R,S-lipoic acid,” or “(±)lipoic acid.” But because of industry conventions – and because, of the fact that, until recently, lipoic acid was only available as the racemate, except for tiny quantities of R(+)-lipoic acid which were made available exclusively to scientists using it for research purposes – conventional “lipoic acid” supplement labels don’t bother to tell you that you’re getting a racemic compound, rather than the pure, natural R(+)-form of the nutrient.
Well, thanks for the terminology lesson, you may think, but so what? We already know that lipoic acid supplements provide health benefits. So does the fact that my lipoic acid is a “racemate” actually affect the value of the supplement? Does the presence of the S(-) form make any real difference?
You bet it does. The S(-)-form that’s taking up 50% of your supplement is not just a weaker cousin of the real thing, like the “other” isomers of alpha-tocopherol in the dl- product. In fact, S(-) lipoic acid is the R(+)-enantiomer’s “evil twin.” When he reported his findings about the opposing effects of the two forms of lipoic acid on the energy-producing powers of mitochondrial particles, for instance, Dr. Guido Zimmer stated that “The S(-)-enantiomer … part of the racemate, which is present as about a 50% impurity [our emphasis], needs to be eliminated.
When you look at the differences between the R(+)- and S(-)- forms of lipoic acid in terms of their effects on the body’s metabolism of blood sugar, or their protective and antioxidant activities, or their effects on mitochondria.(the cellular “power plants” – see Figure 2), and the preliminary evidence on their effects on the aging process itself, we expect you’ll come to agree with Dr. Zimmer and other lipoic acid researchers (see sidebar: What Researchers Say). There are cases where the S(-)-enantiomer is merely less effective than R(+)-Lipoic Acid – and also cases where, at worst, the S(-)-form is just totally ineffective. But as you dig into the lipoic acid story, you’ll also see many cases in which the S(-)-enantiomer actually counteracts the enefits of R(+)-lipoic acid! Learn More About What Researchers Say
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